PCEP allows a path computation client (PCC) to make a request to a path computation element (PCE) for a path or set of paths through a network. The PCE returns a response to the request to the PCC. The PCE has access to the set of paths currently in use, and uses this information in determining the path or paths to assign to the requesting PCC.
Flexi-grid optical networks allow for dynamic allocation of spectrum to channels. As a result, the bandwidth assigned to nominal central channel frequencies can be dynamically adjusted. PCEP does not currently support this dynamic bandwidth allocation.